The most common pyrotechnic formulations used to produce white smoke are based on the reaction between hexachloroethane and zinc to produce zinc chloride and other products. There are other chlorinated organic compounds which have been used in place of hexachloroethane, but one of the products is still zinc chloride. All of these formulations are very efficient smoke producing compositions because zinc chloride is hygroscopic, and absorbs moisture out of the atmosphere, greatly increasing the weight of the smoke produced. The major problem associated with the above cited formulations is the toxicity of the zinc chloride.
There are various other formulations containing elemental phosphorous which have also been used. The smoke produced by formulations of this type contain oxides of phosphorous. These oxides are also hygroscopic, and provide a quantity of smoke that may be several times the weight of the initial phosphorous. While the hydrated oxides are irritants, the main problem with this formulation is the intense fire developed during burning.
Further, there are other typical formulations which have been used but they produce smoke by subliming sulfur. These involve mixing an oxidizer with an excess of sulfur. The heat evolved during the reaction sublimes the excess sulfur present and the reaction results in the formation of sulfur oxides which are toxic.
SUMMARY OF INVENTION
It is an object of this invention to provide a smoke-producing composition which is essentially non-toxic.
Another object of this invention is to provide a pyrotechnic smoke-producing composition which contains 1,4-benzenedicarboxylic acid.